High molecular alcohols such as butanol (C4H9OH), hexanol (C6H13OH), octanol (C8H17OH), and decanol (C10H21OH) are currently synthesized by the oxo method using propylene obtained from petroleum as a raw material. However, as crude oil prices exceeded 50 dollars/barrel in 2004, and the soaring prices of propylene as a raw material led to the rising production cost of high molecular alcohols, the result is a worsened profitability.
The oxo method necessitates the use of deadly carbon monoxide as a raw material in addition to propylene, and the method comprises a complicated, high-pressure reaction which contributes to the rising production costs. Furthermore, the oxo method is unpreferable in view of environmental conservation. As an example, butanol synthesis reactions involve the generation of 2 moles of carbon dioxide as a side product per 1 mole of butanol as shown in reaction (1), and carbon dioxide is a well-known global warming substance.CH3CH═CH2 (propylene)+3CO (carbon monoxide)+2H2O (water)→C4H9OH (butanol)+2CO2 (carbon dioxide)  (1)
Relating to methods for synthesizing 1-butanol from ethanol, both MgO catalysts (“Dimerisation of ethanol to butanol over solid-base catalysts” A. S. Ndou, N. plint, N. J. Coville, Applied catalysis A: General, 251, p. 337-345 (2003)) and zeolite (ZSM-5) catalysts on which alkali metals are supported (“Bimolecular Condensation of Ethanol to 1-Butanol Catalyzed by Alkali Cation Zeolites” C. Yang, Z. Meng, J. of Catalysis, 142, p. 37-44 (1993)) have been used. However, they are not industrially suitable because of their low selectivity.
International Publication No. WO 99/38822 relates to a method for synthesizing 1-butanol with the use of calcium phosphate-based catalysts, although this synthesis method features disadvantages which are associated with the high reaction temperature (as high as 350 to 450° C.) that is involved. For instance, the selectivity of 1-butanol is low; the catalyst regeneration treatment has to be repeated frequently because of the rapid degradation of catalytic property; the durability of devices is decreased; and the fuel cost required for maintaining the reaction temperature is increased.
Thus, there is a clear need for an efficient and clean method of producing high-molecular alcohols from ethanol.